Recycled PMMA particles from milled discs in denture base materials for improved sustainability

Recycling polymethyl methacrylate (PMMA) in dentistry offers a sustainable solution to address the environmental challenges posed by material waste. This study evaluates the feasibility of incorporating recycled (PMMA) particles into heat-cured denture base materials, focusing on the effects of particle size and concentration on flexural strength, surface hardness, and surface roughness.

Recycled PMMA particles, sourced from milling residuals, were classified into fine (< 400 μm) and whole particles and incorporated into virgin PMMA at 10% and 20% weight/weight (w/w) concentrations to form five groups: Control (100% virgin PMMA), Fine 10% (90% virgin PMMA + 10% fine particles), Fine 20% (80% virgin PMMA + 20% fine particles), Whole 10% (90% virgin PMMA + 10% whole particles), and Whole 20% (80% virgin PMMA + 20% whole particles). Flexural strength (n = 10) was evaluated using a three-point bending test, surface hardness (n = 10) was assessed using the Vickers hardness test (VHN), and surface roughness (n = 10) was measured using an optical profilometer. Statistical analysis was performed using two-way ANOVA and Tukey's post hoc test, with p < 0.05 considered statistically significant.

The results showed that fine particle groups (10% and 20%) maintained flexural strength comparable to the control, whereas whole particle groups exhibited significantly lower values (p < 0.05). Surface hardness improved in fine particle groups, with the highest value in the 20% fine particle group, whereas whole particles, particularly at 20%, resulted in the lowest hardness (p < 0.05). Surface roughness remained unaffected across all groups, with values staying within clinically acceptable limits (Ra < 0.2 μm).

These findings suggest that fine recycled PMMA particles can be effectively integrated into denture base materials to maintain or improve specific properties while contributing to sustainability.

This study underscores the potential of recycled PMMA as an environmentally friendly alternative, aligning with global sustainability goals in dental material development.